This is an open-label, ascending-dose study of XMT-1107 administered intravenously over 90 minutes every 21 days (1 cycle). Blood sampling for PK analyses will be performed immediately prior to dosing and after dosing. Adverse events will be graded according to the National Cancer Institute (NCI) Common Terminology Criteria (CTC) version 4.0 (CTCAE v4.0)